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[IEEE 2018 15th European Radar Conference (EuRAD) - Madrid, Spain (2018.9.26-2018.9.28)] 2018 15th European Radar Conference (EuRAD) - Design and demonstration of Linearly-Polarized Transmit-Arrays in X-band
摘要： This paper describes the design and demonstration of planar transmit-arrays operating in X-band with 1-bit phase quantization and based on wideband high efficiency unit cells. The unit cell consists of two identical square patch antennas loaded by C-loop slots and interconnected in their centers by a metalized via hole. The proposed transmit-array achieves a maximum directivity of 25.1 dBi and a gain of 22.8 dBi. Radiation efficiency of 56.3% is also obtained with a 1-dB gain bandwidth of up to 9.2% around 9.85 GHz and very low cross-polarization levels. The beam-steering up to 30° is achieved by tilting the focal source.
关键词： Patch antenna,slot loaded patch,Transmit-array,Antenna arrays,X-band,Unit cell,beam-steering
更新于2025-09-04 15:30:14
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Análise da expans?o térmica volumétrica e das características estruturais de solu??es sólidas de (Pb, Ca)TiO3 entre 150 e 570 K
摘要： Ceramic samples of lead modified calcium titanate (Pb1-xCaxTiO3) with calcium concentration between 0.24≤x≤0.55 were prepared and analyzed in order to determine the structural origin of the negative thermal expansion observed in this ferroelectric system. The Rietveld structural refinement method was used to assess the thermal evolution of the structural parameters using powder X-ray diffraction data collected between 150 and 570 K. Since the Pb1-xCaxTiO3 phase diagram and space groups are still unknown for the temperature range investigated, the structural analyses were based on adjustments of the refinement protocol. The results revealed the existence of a correlation between symmetry transitions and anomalies in the thermal expansion of the unit cell, being such transitions not necessarily of the ferroelectric-paraelectric nature.
关键词： Rietveld refinement method,symmetry transitions,structural analyses,unit cell thermal expansion,ferroelectric ceramics
更新于2025-09-04 15:30:14